One‐Pot Functionalization at C‐2,2′‐Oxidation and C‐3,3′‐Bromination of 3,3′‐ <i>Bis</i> ‐7‐Azaindolylmethane Using NBS/CAN as a Reagent: Synthesis of Brominated 3,3′‐ <i>Bis</i> ‐7‐Aza‐2‐indalones

ABSTRACT The first study of the NBS/ceric (IV) ammonium nitrate (CAN) has emerged as a powerful and efficient reagent for the difunctionalization at C‐2,2′‐oxidation and C‐3,3′‐bromination of 3,3′‐ bis ‐7‐azaindolyl methane to form isolable diastereomers of polybrominated 7‐aza‐ bis ‐2‐indalones as established by 1 H NMR study. The scope of the reaction, characterization of products including XRD technique, and a plausible mechanism for the formation of products are described. Synthetic use of one of the products thus obtained, namely 3′‐methylene bis (3,5‐dibromo‐1‐methyl‐1,3‐dihydro‐2H‐pyrrolo[2,3‐b]pyridin‐2‐one), has been demonstrated by the synthesis of a functionally diverse dispiro[pyrrolo[2,3‐b]pyridine‐3,1′‐cycloheptane derivative by a sequence of reactions (1) zinc/AcOH reduction, (2) allylation, and (3) RCM reaction using Grubbs‐II catalyst.